The obtention of a liquid mixture comprising coal/asphaltenes-fuel oil/heavy crude oil-surfactant-water, is attained through an on-line and/or batch process aided by a static mixer or a tank with shaking devices. This liquid mixture is prepared from an emulsion of fuel oil/water or heavy crude oil/water type O/W, using an anionic surfactant and a polymeric stabilizer. Furthermore, a coal/water mixture is prepared by using the same anionic surfactant. Both fluids are mixed either by adding the coal/water mixture through a progressive-cavities pump or a centrifugal pump provided with open impeller, either to the emulsion, in a tank system with shaking devices or into a pipeline within a continuous system provided with static mixers.
The coal/asphaltenes-fuel oil/heavy crude oil-surfactant-water mixture obtained by both processes has a pseudoplastic rheological behaviour for coal concentrations from 5% to 35%, its viscosity is lower than that of the samples used for its preparation, is stable for several weeks, has a calorific power from 11000 to 13000 BTU/lb, being higher than that of the coal/water mixtures and is suitable for pipeline transportation. The rheological behaviour of these liquid mixtures is originated in the bi-modal character of the particle-size distribution of their components. The finest particles, in this case emulsionated fuel oil particles, perform the lubrication function, being placed within the interstitial spaces between the particles with bigger diameters, that is, the coal particles.
U.S. Pat. No. 3,941,552, 1976 and U.S. Pat. No. 4,326,855, 1982, to Eric C. Cotell, and others, concern to combustion, profitability and stability, the formation of a triple mixture with coal-fuel oil-water with additives of certain composition (50%-40%-10%) obtained through high-energy ultrasonic shaking, 38-54 watts/cm.sup.2 and 15000 to 20000 Hz, which, in the shaking moment, fractionates the coal particles up to gel-sizes; these small sizes and use of too heavy fuel oils, grant the triple mixture an excellent stability but admitting a high viscosity
In this case, the coal particles attain formation of two types of bonds or links: coal to coal bonds through water bridges and coal to coal bonds through fuel oil and additives links, giving as overall result a net structure, very stable but simultaneously too viscous, as clearly exposed in U.S. Pat. Nos. 4,403,997, 1983, and 4,401,437, 1983, to Leonard E. Poetshke, where coal concentration is increased up to 70% and proportions of fuel oil and water are reduced to 10% and 20%, respectively, using the same ultrasound technique used for preparing the mixture.
In UK Patent No. 2 165 858 to Gererd Antonini, 1986, released or exhausting water, present in the triple mixture as emulsionated particles within a continuous phase of fuel oil (direct emulsion) is used to facilitate its transportation. When this direct emulsion is treated by cutting forces, water is released and migrates and stays in the mixture-pipe interface and generates a lubricating film between those two elements; this film means a lower energy requirement for transportation, as if the mixture had a lower viscosity.
The Antonini's mixture is composed by 15% water, 40% fuel oil and 45% coal, with a particle size allowing 80% passing through a 200 mesh (74 microns); however, the mixture exhibits high viscosity and causes certain troubles when passing through burners.
U.S. Pat. No. 4,842,616, 1989, to Marcel Verhille, describes use of inverse emulsions, with low viscosity mixtures, because of their high water proportion, among 45% to 50%, showing these mixtures a non-defined particulate system for disperse phases as base for viscosity and stability, as offered by the new technology. On the other hand, a mixture with 50% water, does not have a high calorific power, as shown by triple mixtures as described in the herein shown technology, which makes them suitable to be used as fuels exhibiting excellent characteristics.
For gaining stability, the prior art employs three different additives: a polymeric emulsifier based on polyoxyethylene HLB 17, very expensive, besides a colloid, xanthate gums and an electrolyte, all under vigorous shaking. On the contrary, the technolgy described in the present patent application, only uses low-cost additives, locally manufactured with ECOPETROL-ICP technology, with no gums nor electrolites, and does not require an extreme shaking rate, usually the range from 100 to 300 rpm being enough. For the new technology, the particle size, for both the coal and the emulsion reaches great importance.